...IMHO the price difference reflects the higher quality, function and build of the CZ rifle. Having owned 2 SKS's [one fixed mag and one "D" model both chinese] I feel qualified to say I have played the "Norinco-lottery"

and the only good buy in a chinese SKS is the standard fixed mag model for under 200$. The SKS "D" is NOT worth the higher price it commands, mine was an absolute roach with feed issues and the scariest most unpredictable "creepshow" of a trigger I have experienced on any firearm, I don't know if thats the case with many "D"'s but I paid 400$ dollars too much for that P.O.S.

That being said my regular fixed mag SKS goes bang everytime I pull the trigger and is a rugged, reliable [if somewhat crude] shooter well worth its price tag of 150$.
I've already got too long winded of a post to rave too much about the CZ, but when I bought mine from Lever arms a couple years back they had not gained the popularity they enjoy now. I remember first off being attracted to the CZ by its looks, and then when I handled it I loved its lightweight, pointability and ergonomics. When I got it home and disassembled it I was impressed by the quality of the parts, reciever not stamped steel, last shot hold open, ease of take-down etc. Then when I shot it I immediately knew It was worth the money

. It has a decent, clean breaking trigger,cycled flawlessly and was more accurate then either of my SKS's.
I, along with most others love my CZ-858 and although I have heard of some cycling issues " 858-gremlin" mine has functioned flawlessly for close to 2500-3000 rounds now. This rifle has become a darling of the aftermarket lately as well with everything and anything available to suit personal tastes.
To make a ridiculously long post short, The CZ-858 package in my opinion is a stellar improvement over the chinese or Norinco SKS and a superior product.
Just to add one more thing to think about, if you do decide to pony up the 650$ 'ish for an 858 package for a slight bit more you could get a Ruger mini-thirty. IMHO they are slight step above the 858 with comparable accuracy but a very nice factory fit and finish, don't be scared by the folks who downtalk the Mini, I have shot more than one and they are a decent auto-loading rifle for the money.
Good luck with whatever you choose,
Mad Mikey.
